This invention deals generally with the collection and discharge of exhaust gases from motor vehicles operating within a building, and more specifically with a duct system installed below the floor of a garage and the wheeled hose dolly which travels along the buried duct.
The requirement that motor vehicle exhaust gases be removed from any enclosure within which a vehicle is operating is quite obvious since the carbon monoxide emitted from a vehicle exhaust is toxic. The existing devices to accomplish the direct discharge of such vehicle exhaust gases to the outside of the building are quite varied. They include everything from a simple flexible hose slipped over the tail pipe and through a hole in a garage door to multiple stations with blower driven overhead exhaust ducts from which flexible hoses hang down for attachment to the vehicles' exhaust pipes.
Another sizeable group of such exhaust systems includes the those which allow the hose to be moved along the length of the permanent overhead exhaust duct even when connected to a vehicle's exhaust. In such systems a vehicle's emissions can be discharged even while the vehicle moves through the building, and it permits the connection of the hose to vehicles of various sizes or in multiple locations. This movement of the hoses along an overhead exhaust duct is generally accomplished by means of a hose trolley which hangs from the exhaust duct which has a flexible seal to close a slot through which a pipe of the hose trolley extends into the duct.
In such arrangements, the flexible seal is spread open by the hose trolley as it moves along the duct, and the seal closes behind the trolley as it passes. Fortunately, the suction of the exhaust blower, which is pulling the vehicle exhaust fumes into the duct, also prevents those fumes from leaking out of the seals around the trolley or out of the many joints in the ducts required for a system of any size.
These exhaust systems with movable trolleys and multiple hoses hanging from the overhead dusts have several obvious disadvantages. Certainly the most obvious is the considerable visual clutter which they present. If a service garage has several bays on both sides of an access aisle, that means there will be a large flexible hose hanging down from the room's ceiling near the access aisle at the end of each service bay, and that two large ducts and a manifold connecting them will be suspended just below the room's ceiling. Along with the visual clutter, the overhead ductwork forces the construction of a taller building to maintain any given clearance height above the vehicles using the building.
Another disadvantage of the overhead systems arises from the location of the exhaust of many vehicles. When the tail pipe of a vehicle is located near the bottom of the vehicle, as it is for most automobiles and small trucks, and for some larger vehicles such as fire trucks, the pressure drop within the long hose reaching from near the ceiling almost to the floor can be quite high. Since this pressure drop is usually the greatest in the system, this forces the system's blower to be larger and more powerful than would be required if a lower pressure drop could be attained with shorter hose connections to the vehicle.
A more subtle disadvantage of the overhead duct system involves the occasional circumstance when a vehicle is driven out of the garage without first detaching the exhaust hose. With an overhead installation, if the hose breaks or the trolley falls, the hazards from the falling objects are quite severe. The hazard is clearly even greater if the misuse causes a part of the overhead ducts to break and fall.